Prevent me from duplicate adding in same bookmark folders

Hello,

Scenario of the problem:

For instance, I added a site to my bookmark manager 1 hour a go. Now I see the website again and forgot that I added it before! so I add it again in the same folder of bookmarks. There is no notification for me that I added it before, so I have duplicates of bookmarks in them same folder. I did it very much and I don't know how to prevent this duplicate bookmarks. All other browsers show me that I added the bookmark before with a star sign or when I added them again they notice me. Please help me in solving this problem.

Notice: All the search result about my problem is about iCloud, but my question is not about iCloud.